Article Constraining features in the inflationary potential with future weak lensing data Ivan Debono 1 Citation: Debono, I. . Universe 2021, 1, 0. https://doi.org/ Academic Editor: Firstname Lastname Received: Accepted: Published: Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and in- stitutional affiliations. Copyright: © 2021 by the author. Submitted to Universe for possi- ble open access publication under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://cre- ativecommons.org/licenses/by/ 4.0/). 1 Paris Centre for Cosmological Physics, Universit´ e de Paris, CNRS, Astroparticule et Cosmologie, F-75006 Paris, France; ivan.debono@in2p3.fr Abstract: The next generation of large-scale structure surveys should probe primordial physics 1 beyond the overall shape and amplitude of the main, smooth and slowly-changing part of the 2 inflaton potential. Using the specifications for the upcoming Euclid survey, we estimate the 3 constraints on the inflation potential beyond its established slow-roll behaviour. We use mock 4 Euclid and Planck data from fiducial power spectra using the Wiggly Whipped Inflation (WWI) 5 framework to generate features in the primordial spectrum. We include both Euclid cosmic shear 6 and galaxy clustering, with two setups (Conservative and Realistic) for the non-linear cut-off. 7 Using Markov chain Monte Carlo simulations, we find that the addition of Euclid data gives an 8 improvement in constraints in the WWI potential, with the Realistic setup providing marginal 9 improvement over the Conservative setup for most models. This shows that Euclid may allow us 10 to identify oscillations in the primordial spectrum present within intermediate to small scales. 11 Keywords: cosmology; inflation; weak lensing; cosmic microwave background 12 1. Introduction 13 Observations in cosmology have now caught up with theory, and physics at the largest 14 cosmological scales has been probed by full-sky surveys. Data from various observations 15 enable us to measure the parameters in our cosmological model with increasing precision. 16 The Λ cold dark matter (ΛCDM) concordance model can fit different astrophysical 17 datasets with only six parameters describing the mass–energy content of the Universe 18 (baryons, CDM and a cosmological constant or constant dark energy) and the initial 19 conditions. Any deviations from ΛCDM are too small compared to the current obser- 20 vational uncertainties to be inferred from cosmological data alone, but some additional 21 parameters cannot yet be ruled out. 22 There are three big open questions in modern cosmology 23 1. Dark matter, whose nature is still unknown; 24 2. Dark energy, or the component causing the accelerated expansion of the Universe; 25 3. Conditions in the very early Universe. 26 The data are compatible with a Universe filled with dark matter and cosmological constant, 27 with a smooth primordial power spectrum. But do not exclude dynamical dark energy. 28 Nor do they exclude features in the primordial power spectrum 29 This paper is a companion to [1], in which the authors focussed on the physics of 30 the primordial Universe, and examined the ability of Euclid to provide information about 31 features in the primordial power spectrum beyond that which Planck has provided. Here 32 we show how the inclusion of information from large-scale structure at smaller scales can 33 improve constraints from Euclid. 34 In order to explore the features we use Wiggly Whipped Inflation (WWI; [2]), 35 which can generate a wide variety of primordial power spectra with features at different 36 cosmological scales. 37 We use the best-fitting Wiggly Whipped Inflation models obtained using Planck to 38 create fiducial cosmologies and data for Planck and Euclid. We use Markov chain Monte 39 Version February 10, 2021 submitted to Universe https://www.mdpi.com/journal/universe